LMC6001: Noise appeared on pA-nA a transimpedance amplifier

Change the feedback to 8pF, should give a Butterworth at about 28kHz BW

This is a really old part with very poor input voltage noise, newer parts might do better noise wise, 

Hello k s,

Michael has provided good, useful advice for improving your transimpedance circuit performance. Please consider his recommendations.

Additionally, your LMC6001 transimpedance amplifier (TIA) circuit has a transimpedance gain of 1 million, which is very high. Fifty or 60 Hz line frequency fields in your test circuit location can end up being picked up by the circuit board/ wiring and end up being amplified by the TIA circuit.

It is best to enclose your TIA circuit in a metal enclosure and power it from the 9 V battery mounted inside the enclosure. We often use a small aluminum box, or even an unused paint can as the enclosure for test purposes. An opening in the enclosure can be provided for the photodiode so that it can receive the light from the light source, but keep the opening to a minimum. The output of the TIA should be routed to a coaxial connector mounted to the metal enclosure. A coaxial cable can then be used to bring the TIA output signal from the output connector to any circuit that follows.

Regards, Thomas

Precision Amplifiers Applications Engineering

Hi k s,

the output of LMC6001 saturates:

ks_lmc6001.TSC

Add a negative supply voltage or add bias voltage to prevent the output of LMC6001 from saturating:

Also, as aleady mentioned by Thomas, shield the circuit with a metal enclosure and connect it to signal ground.

Kai

PS: Sorry Thomas, I didn't see your post :-)

Hi ,Michael,

Thank you for your support.
I change the capacitance to 10pF (I did't have 8pF).

I have one question.
In this case, the circuit works safety with feedback capacitance lager than 8pF, right?
If I use 100pF, it will only decrease the BW, right?

Sincerely,

K.S

Dear Thomas,

Thank you for your support.
Your good explanation is very easy to understand, and I convinced.
I will try to enclose in a metal box within a few days.

And, I would like to convert sub-pA-order current from a photodiode to sub-μV-order voltage.
If you have an idea, would you teach me?

Sincerely,
K.S

Dear Kai,

Thank you for your support.
Your advice is helpful.
I confirmed that the simulation result using your model.

I would like to use the circuit by using a battery.
In this case, how can I get negative voltage?

Sincerely,
K.S

KS, use the LM7705